This invention relates to internal combustion engines. More particularly, this invention relates to cylinder heads and rocker arm assemblies for internal combustion engines.
Internal combustion engines often have a fulcrum rocker assembly for operating the intake and exhaust valves. The push rod which engages the rocker assembly is typically held in alignment by a push rod guide plate. The guide plate is required because in typical rocker arm assemblies, the bearing surface on the rocker arm which engages the fulcrum bearing surface is semi-spherical in shape, so that the rocker arm may turn laterally. The push rod guide plate tends to prevent such lateral rotation, but at increased expense.
It is known to prevent rotation of the fulcrum by providing a squared-off fulcrum block portion having at least two substantially parallel sides. These sides may be retained by a retainer, which is fastened to the cylinder head. In other prior art engines, the fulcrum block is retained by a pair of spaced alignment ribs integrally formed with the cylinder head. These alignment ribs are created by machining the cylinder head after the cylinder head has been cast; a slot or groove is formed in the pedestal portion of the cylinder head by machining, with the ribs being spaced on opposite sides of the groove. Of course, this process is relatively expensive since a machining step is required to form the ribs.
In fulcrum rocker assemblies, there is a small gap or lash between the end of the push rod and the rocker arm. If the lash is too large, the engine will tend to clatter and either the push rod or the rocker arm may wear prematurely. Therefore, it is desirable to adjust the amount of lash so that the lash stays within acceptable limits.
Typical prior art engines use self-adjusting hydraulic lash adjusters. However, these hydraulic lash adjusters are relatively complex and expensive to manufacture and assemble.
Therefore, it is desirable to reduce the cost of an internal combustion engine by both reducing the number of components and the number of machining and assembly steps.